This invention relates to optically excited lasers and more particularly to optically pumped lasers that use high radiative efficiencies of electronically excited, rare gas dimers.
It is well known in the laser art that laser systems include three main components; the laser medium, which may be gaseous or a solid; the laser cavity which includes reflective surfaces; and a means for pumping the laser medium to an excited state. The laser medium may be optically pumped, or electronically or chemically excited and may be operated continuously or pulsed. Such laser systems are operated at room temperature and very low temperature such as a liquid nitrogen temperature. Further, laser systems may be operated in or outside the visible spectral region. They may be high power or low power. Such laser systems have been developed using a variety of elements, compounds, gases or fluids and all have one thing in common, they emit coherent radiation. Laser oscillation in the B.fwdarw.X band of XeF at 350 nm has previously been demonstrated for electron beam, e-beam sustained, and discharge pumping of rare-gas-NF.sub.3 (or F.sub.2) gas mixtures. Efficiencies for this laser have been limited to .ltorsim.3% for e-beam operation (at room temperature) using Ne as the diluent and to 1% for excitation by a fast electric discharge. However, the ability of optical pumping to populate an electronic state of interest selectively has not preciously been applied to the excitation of the rare-gas-halide lasers.
Both rare-gas-halide and rare-gas-excimer radiation have been successfully utilized as optical pumps for lasers in the near-infrared to ultraviolet region of the spectrum. Rare-gas-halide fluorescence and laser radiation have been used to excite the I(1.3 .mu.m) and In (0.451-.mu.m) atomic lasers and the HgBr photodissociation laser. The attractive features of the rare-gas excimers as sources of incoherent pump radiation for electronic-state lasers have been pointed out by Murray and Rhodes, J. Appl. Phys., Vol. 45, p. 5041, 1976, who investigated the use of Xe.sub.2 * or Kr.sub.2 * vacuum-ultraviolet (VUV) fluorescence as excitation sources for amplifiers (operating on the auroral and transauroral lines of selenium and sulfur) for eventual use in thermonuclear fusion studies. In particular the high fluorescence efficiences (.about.50%) projected for the rare-gas excimers both experimentally and theoretically point to electron-beam-excited rare-gas plasmas as potentially efficient optical pumps for visible and ultraviolet lasers.
Since the initial demonstration of lasing from HgCl and HgBr utilizing electron-beam pumping, a surge of activity on the mercury-halide laser family has produced stimulated emission from HgCl and HgBr with e-beam-sustained and uv preionized discharge excitation of rare-gas/Hg/Cl.sub.2 or CCl.sub.3 Br, mixtures. Unfortunately, chemical reaction of the mercury and halogen donor in these systems has forced the use of flowing gas mixtures or fresh gas fills for each laser pulse.
Recently, several investigators have successfully induced lasing on the B.fwdarw.X band of HgX(X=Cl, Br, or I) by dissociating the salt HgX.sub.2 by electron impact. One of the attractive features of these dissociation lasers over the Hg/halogen donor chemical laser has been pointed out by Schimitschek and Celto, Opt. Letters, Vol. 2, page 64, 1978, who noted that the salt molecules appear to be recycled following dissociation and subsequent lasing. For example, EQU HgCl(X)+Cl+He.fwdarw.HgCl.sub.2 +He+.DELTA.E.
This process has presumably enabled these devices to operate for long periods of time without any noticeable degradation of the output power/pulse.
This invention has been set forth in two publications "VUV Pumped HgCl LASERS", by J. Gary Eden, Appl Phys. Letters, Vol. 33, pp. 495-497, Sept. 15, 1978; and "XeF(B.fwdarw.X) Laser Optically Excited by Incoherent Xe.sub.2 * (172-nm) Radiation", by J. Gary Eden, Optics Letters, Vol. 3, pp, 94-96, September 1978. These publications are incorporated herein by reference.